Meteorites 26 October 2015

Chondrite

Achondrite

Martian

Chixulub, Yucatan penninsula, Mexico Gravity map of buried structure 180 miles across; 65 millions years old Identified in early 1990s with seismic data, after 10 year ‘search’

Tunguska, Siberia, June 30, 1908 Black and white photos taken during field expedition in 1927; color photo taken in 1990

Jackson Hole Fireball, August 10, 1972

Potentially Hazardous Asteroid Threat Size-frequency diagram for impacting objects ~100 tons of meteroritic dust falls each day 50 m impactor once per 1000 yr (local effects) 500 m impactor once per million years (regional effects) 5 km. impactor once per 100 million years (global effects)

Hoba Iron 3m x 2m x 1m; 60+ tons Found 1920, Namibia No crater, classified ataxite

Ordinary Chondrites (S Asteroids?)

Three Views of Vesta Hubble image, model and color-shaded topography Largest member of V class of asteroids (vestoids) Spectral variations consistent with HEDs

What were the processes and products in the early Solar System (Meteoritics, 2004) Impact features on all planetary surfaces; planets formed by accretion of planetesimals from a turbulent solar nebula Much mixing of components; completed in 5-10 million years ‘Residual’ debris forms asteroid belt; Kuiper belt, Oort cloud

Meteor showers Time exposure image, tracking stellar motion Stars stay still, meteorites make trails

The Peekskill (NY) Fireball

P Jenniskens et al. Nature 458, 485-488 (2009) Macroscopic features of the Almahata Sitta meteorite. P Jenniskens et al. Nature 458, 485-488 (2009)

Chondrites Rocky, inhomogeneous, contain round “chondrules” Microscope image

Iron meteorites: from core of differentiated asteroids

Stony-Iron meteorites - the prettiest Crystals of olivene (a rock mineral) embedded in iron From boundary between core and mantle of large asteroids?

The main points: Meteorites Each year the Earth sweeps up ~80,000 tons of extraterrestrial matter Some are identifiable pieces of the Moon, Mars, or Vesta; most are pieces of asteroids Meteorites were broken off their parent bodies 10’s to 100’s of million years ago (recently compared to age of Solar System) Oldest meteorites (chondrites) contain interstellar dust, tiny diamonds made in supernova explosions, organic molecules and amino acids (building blocks of life) Direct insight into pre-solar system matter, solar system formation